UCN-CEAZA
Genetic signatures of rafting dispersal in algal-dwelling brooders Limnoria spp. (Isopoda) along the SE Pacific (Chile).
Haye, P., Varela, A., & Thiel, M.
ABSTRACT: Brooding marine isopods of the genus Limnoria inhabit and feed on kelp holdfasts and wood. These substrata have high floating potential, making these species ideal organisms to study the effects of rafting-mediated connectivity on the population structure of brooders living on rafting substrata. It is hypothesized that rafting leaves particular genetic signatures such as low differentiation among distant local populations and absence of isolation by distance (IBD) at a macro-geographic scale (thousands of km). Using cytochrome oxidase I (COI) sequences, we tested the effects of rafting-mediated gene flow with respect to genetic differentiation on L. quadripunctata (from wood and also the holdfasts of the giant kelp Macrocystis pyrifera) and L. chilensis (mainly from the bull kelp Durvillaea antarctica) sampled across 2400 km of the Chilean coast. Analyses of COI data for both species indicated low differentiation between distant locations along the Chilean coast and lack of IBD, bearing the expected genetic signatures of rafting dispersal. Phylogenetic analyses were performed with COI and the nuclear gene 28S to place the genetic diversity of Chilean Limnoria spp. into a wider geographical context. Both markers revealed that L. quadripunctata from Chile is a sister clade to other Limnoria spp. analyzed (L. chilensis, L. segnis, and L. stephenseni), which mainly inhabit D. antarctica. L. chilensis from Chile and subantarctic islands form a tight monophyletic group. Phylogenetic and phylogeographic analyses show that along the studied area, L. quadripunctata and L. chilensis have the genetic signatures of relatively recent or ongoing rafting.
Año: 2012
Palabras claves: Peracarids, Rafting, Biogeography, Mitochondrial DNA, COI, 28S, Phylogeny, Phylogeography
Referencia APA: Haye, P., Varela, A., & Thiel, M. (2012). Genetic signatures of rafting dispersal in algal-dwelling brooders Limnoria spp. (Isopoda) along the SE Pacific (Chile). Marine Ecology Progress Series, 455, 111-122.
Herbivorous amphipods inhabit protective microhabitats within thalli of giant kelp Macrocystis pyrifera.
Gutow, L., Long, J., Cerda, O., Hinojosa, I., Rothäusler, E., Tala, F., & Thiel, M.
Many small marine herbivores utilize specific algal hosts, but the ultimate factors that shape host selection are not well understood. For example, the use of particular microhabitats within algal hosts and the functional role of these microhabitats have received little attention, especially in large algae such as kelps. We studied microhabitat use of the herbivorous amphipod Peramphithoe femorata that inhabits nest-like domiciles on the blades of giant kelp Macrocystis pyrifera. The vertical position of nest-bearing blades along the stipe of the algal thallus and the position of the nests within the lateral blades of M. pyrifera were surveyed in two kelp forests in northern-central Chile. Additionally, we conducted laboratory and field experiments to unravel the mechanisms driving the observed distributions. Peramphithoe femorata nests were predominantly built on the distal blade tips in apical sections of the stipes. Within-blade and within-stipe feeding preferences of P. femorata did not explain the amphipod distribution. Amphipods did not consistently select distal over proximal blade sections in habitat choice experiments. Mortality of tethered amphipods without nests was higher at the seafloor than at the sea surface in the field. Nests mitigated mortality of tethered amphipods, especially at the seafloor. Thus, protective microhabitats within thalli of large kelp species can substantially enhance survival of small marine herbivores. Our results suggest that differential survival from predation might be more important than food preferences in determining the microhabitat distribution of these herbivores.
Año: 2012
Palabras claves:
Referencia APA: Gutow, L., Long, J., Cerda, O., Hinojosa, I., Rothäusler, E., Tala, F., & Thiel, M. (2012). Herbivorous amphipods inhabit protective microhabitats within thalli of giant kelp Macrocystis pyrifera. Marine Biology, 159(1), 141-149.
Gene expression analysis in Mytilus chilensis populations reveals local patterns associated with ocean environmental conditions.
Núñez-Acuña, G., Tapia, F., Haye, P., & Gallardo-Escárate, C.
Marine ecosystems involve relationships between genomic interactions of marine populations with shared biogeographic ranges and the environmental conditions. These relationships, studied mainly through neutral DNA markers, are not always consistent with actual biogeographic patterns or the evolutionary history of marine species. In addition, increased information at functional genomic level from non-model species allows the study of adaptive responses in marine populations. This work reports local transcriptomic patterns in populations of the mussel Mytilus chilensis and their correspondence with oceanographic variability in southern Chile. Analysis of gene expression patterns was conducted through qPCR of seven candidate genes involved in the response to environmental stress (HSP70, HSP90), iron metabolism (Ferritin), pathogens (Mytilin B, Defensin) and oxidative stress (SOD-CuZn, Catalase) in at five study sites located in southern Chile, from Valdivia (39°56′S–73°36′W) to Melinka (43°52′S–73°44′W). Multivariate and correlation analyses were used to assess the relationship between levels of individual gene expression and site features characterized using satellite data on surface temperature, chlorophyll concentration and total suspended sediments. Two main groups of sites with differential patterns of gene expression were identified. Individuals exposed to higher temperatures showed an overexpression of HSP70, HSP90 and Ferritin genes. The expression of SOD-CuZn and Catalase was correlated with local chlorophyll-a (i.e. food availability for mussels), although with opposite correlations. In addition, Mytilin B showed higher levels of expression in areas with higher freshwater influence. Patterns of gene expression across the region of interest suggest that spatial variability in environmental conditions induce phenotypic changes in different populations of the same mussel species. In addition, the analysis of expression patterns in candidate genes can reveal local patterns in populations where other molecular markers show no genetic structure.
Año: 2012
Palabras claves: Gene expression; Mytilus chilensis; Adaptative response; Environmental stress; Thermal tolerance; Sea surface temperature
Referencia APA: Núñez-Acuña, G., Tapia, F., Haye, P., & Gallardo-Escárate, C. (2012). Gene expression analysis in Mytilus chilensis populations reveals local patterns associated with ocean environmental conditions. Journal Of Experimental Marine Biology And Ecology, 420-421, 56-64.